1. Field of the Invention
This invention relates to brushless motor driving device, and more particularly to an improvement of the brushless motor driving device in which generates previously a waveform of a driving current.
2. Description of the Prior Art
With reference to this type of brushless motor driving device, considered workable hitherto is such device as is constructed to carry a driving current of sine waveform which is stored beforehand in a predetermined memory at a given timing to a coil of each phase constructing a brushless motor.
Meanwhile, the torque of a motor is generally calculated as a result obtained from multiplying a coil current by an interlinked flux. The interlinked flux of a coil however does not form an accurate sine wave practically, but forms a wave having an odd degree harmonic component. Accordingly, a problem to arise therefrom is such that if a current carried to the coil is sine wave, a torque waveform of the motor obtained through the current in sine wave and the interlinked flux in a waveform different therefrom will not be unified to cause a pulsation.
To solve the aforementioned problem, a conceivable method is such that a driving current waveform is generated at the time of manufacturing process adaptationally to an interlinked flux of individual motors without using a sine wave, and is stored in a memory, however, trial and error will be necessary for setting an optimal current waveform at every type of motors, thus complicating the work.